There are many industrial processes that generate waste water or other liquids that must be filtered and purified prior to returning the water to the environment or reusing the water. For example, in the oil and gas industry, wellbore drilling, completion, and production can generate contaminated liquids. To enhance wellbore production, liquid is frequently injected at high pressure into subterranean rocks, boreholes, etc., to force open existing fissures in the formation and enable extraction of oil or gas from the wellbore. This process is referred to as “hydraulic fracturing” or “fracking,” and often generates waste water (referred to in the industry as “flowback” water) that includes sediment and other contaminants. Flowback water may be produced in large quantities (about 40-50 barrels per day) within a short span of time after a hydraulic fracturing job is completed. Flowback water mainly consists of clay particles, chemical additives, dissolved metal ions, and total dissolved solids (TDS) with its content and concentration depending upon geography. Reusing this water continues to be a great industry challenge.
New technology is needed to treat flowback water so that it can be reused directly or blended with fresh water. On-site treatment and recycling is a desired solution, and several technologies have been explored for the water treatment process including the use of chemical additives and pH adjustment to cause precipitation of metal sulfides. However, these methods do not remove all the salt contaminants. Other alternatives involving thermal evaporation techniques are not economically viable on a large scale. Additionally, technologies utilizing reverse osmosis have drawbacks in that existing membranes can be easily fouled at higher contaminant concentrations.
Conventional filtration membranes, such as those found in spiral-wound filters, comprise of a variety of materials including fluoropolymers, polyamides, polyethersulfones, and polyacrylonitriles. However, such materials can be limited due to their physical properties.